The mucosa of the respiratory tract, if desquamated by injury or infection, regenerates rapidly. The purpose of the present study is to demonstrate the morphological process of early stage respiratory mucosal regeneration in rats.The tracheal mucosa of 54 adult rats of both sexes was removed by curetting through tracheostoma.Each time, from 1 hour to 12 hours after curetting, specimens were collected from the injured area of the trachea of 4 rats for TEM and SEM study. In addition, vascular network casts for SEM were made each time by infusion with artificial resin through the aortic arch of 2 rats.1) As early as 2 hours after curetting, the surviving epithelial cells (mainly the basal cells) began to migrate from the wound margin. This migration was still continuing 12 hours after curetting, although no increase in mitosis was found yet in the surviving epithelial cells.2) Also beginning one hour and 30 minutes after curetting, the injured blood vessels formed terminal "blind" branch vessels (mainly capillaries and veins). Four hours and 30 minutes after curetting, many bud-like processes were observed at the floor and margin of the curetted wound. Six hours after curetting, these processes grew into "blind" branch capillaries, and areas of these capillaries anastmosed with the neighboring capillaries or veins. Twelve hours after curetting, new vascular networks were formed in the areas of the new vessels (mainly capillaries and veins), but the arrangement of vessels was irregular.No increase of mitosis was found in the lamina propria and submucosal layer within 12 hours after curetting.
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